I voted Obsidian, but this is assuming TES development doesn't mess with Eternity dev time. If it would, that would push my vote over to Bioware. They make generic cookie-cutter RPG stuff, but at least I can understand the lore.
I've played TES since Daggerfall and I still can't follow wtf is going on. That, and the previously mentioned Dawnguard stuff. That would have been a good staging point for some player controlled Werebear goodness and past Vampire lore to emerge.
Instead it was reruns of Gargoyles with a spattering of new perks.
~ Sincerely Yours, Rev. Edward E PLURIBUS DUDEINUM